qt: Remove hidden columns in coin control dialog

Summary:
Store the data in specific roles instead of storing it as text in hidden columns.

Backport of Core PR14828

Test Plan:
ninja && ninja check

Run src/qt/bitcoin-qt and verify that the empty columns at the end of the table are no longer there, in the Coin Selection dialog.

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7798